Numerical investigation of a perovskite-MXene functionalized D-shaped photonic crystal fiber-based SPR sensor for refractive index sensing

D -shaped fibers offer a practical platform for depositing plasmonic and functional materials, enabling efficient coupling of optical energy into the sensing medium. In this work, a highly sensitive perovskite–MXene-based D -shaped photonic crystal fiber ( D -PCF) surface plasmon resonance (SPR) sensor is proposed and numerically characterized using the finite element method (FEM). Silver is employed as the plasmonic material due to its excellent SPR response, while perovskite and MXene layers are incorporated to enhance light–matter interaction and improve sensing performance owing to their favorable optical and electrical properties. The effects of key structural parameters, including the thickness of each functional layer and the air-hole diameter, are systematically investigated to optimize the sensor performance. Among the evaluated plasmonic materials, silver exhibits superior sensitivity compared with the other materials. The proposed PCF-based SPR sensor demonstrates low confinement loss and enhanced sensing characteristics over an analyte refractive index range of 1.16–1.24. Numerical results show a maximum wavelength sensitivity of 5000 nm/RIU and an amplitude sensitivity of 210 RIU⁻¹ . These findings indicate that the proposed sensor has strong potential for chemical sensing, biosensing, and other refractive-index-based sensing applications.